Method and device for measuring the dimensions of the transversal cross-section of pipes

Abstract

A device for measuring the overall dimensions of the transversal cross-section of pipes made of thermoplastic material fed along a rectilinear direction, means for detecting the position, on a Cartesian plane, of four points identified on the outer surface of the pipe, the points lying on four respective half-lines originating in the origin of the Cartesian plane.

1 . A method for measuring the dimensions of the transversal cross-section of a pipe made of thermoplastic material fed along a rectilinear direction, comprising the steps of:
 defining a Cartesian plane having its origin inside the transversal cross-section of the pipe to be measured and being substantially perpendicular to the rectilinear direction of feeding the pipe,   preparing outside the pipe four distance measuring sensors along respective half-lines originating from the origin of the Cartesian plane, each of the half-lines forming, with the axis of the X-axis of the Cartesian plane, respective angles which are separate from each other,   measuring the distance of each of the sensors from the outer surface of the pipe, the distance being measured along the half-lines to define the coordinates on the Cartesian plane of the intersection points of the half-lines with the outer surface of the pipe,   calculating the equation of the ellipse passing through the intersection points, thereby defining the shape and the position of the pipe relative to the sensors and to the Cartesian plane.   
     
     
         2 . The method according to  claim 1 , wherein the step of preparing the sensors along respective half-lines comprises the step of selecting the half-lines in such a way to respect the condition by which at the most three of the half-lines constitute bisectors of respective quadrants of the Cartesian plane. 
     
     
         3 . The method according to  claim 1 , wherein the step of preparing the sensors comprises the step of positioning the sensors along a circumference having the centre in the origin of the Cartesian plane. 
     
     
         4 . A device for measuring the dimensions of the transversal cross-section of pipes made of thermoplastic material fed along a rectilinear direction, comprising:
 means for detecting the position, on a Cartesian plane, of four points identified on the outer surface of the pipe, the points being separate from each other and lying on four respective half-lines originating in the origin of the Cartesian plane,   a processing unit configured for calculating the equation of the ellipse passing through the four points the position of which is identified by the detection means.   
     
     
         5 . The device according to  claim 4 , wherein the position detection means comprise four distance measurement sensors positioned outside the pipe along the half-lines originating from the origin of the Cartesian plane. 
     
     
         6 . The device according to  claim 5 , wherein the distance measurement sensors are optical sensors. 
     
     
         7 . The device according to  claim 5 , wherein the distance measurement sensors are ultrasound sensors. 
     
     
         8 . The device according to  claim 4 , wherein the half-lines are such as to respect the condition by which at the most three of the half-lines constitute the bisectors of respective quadrants of the Cartesian plane.